Dear Tom,

I own a 2004 Chevy Aveo. The other day I got a flat tire and I had the spare installed. It’s a fake tire (one of those “donut” spares). I haven’t had a chance to buy a new tire yet, and I want to know how long can I drive before I replace it with a real tire. Funds are tight right now.

Sarah from Burlington, VT

Sarah,

Check your owner’s manual for an exact recommended mileage for the spare tire. Seventy miles is the rule of thumb. These tires are not designed for long-range service. They are made to get you to a garage to have your tire either repaired or replaced. Driving on it for an extended period of time under regular driving conditions will result in a blowout in short order, so get a safe tire on your car immediately. Maybe you can find a reasonably priced used tire if it has to be replaced.

Tom

Wow, Sarah asks the kind of question that seems to crop up more and more these days. I guess the slow economy has everyone strapped for extra cash to meet unexpected events. Let’s take a look at Sarah’s concern in detail.

How Long Can I Drive With A “Donut” Spare?

Donut spare tires are not made for extended service. They have no tread to speak of; the carcass or body of the tire is not reinforced and there is no tread belt to protect it from projectiles and road imperfections. The tire is designed simply to get you to a repair facility. Most of these tires offer a maximum life of 70 miles.

Do Donut Spares Affect The Braking Or Suspension System?

You may notice poor cornering, handling, and braking characteristics. The donut spare has a smaller footprint than a conventional tire, which translates into diminished braking and handling. With the donut spare in place, you may find that, when braking, the vehicle dips to the side where the donut was mounted. Also, you may notice the vehicle pulling to that side.

Why Do Carmakers Put These Spare Tires In Cars?

The use of donut spares is a cost and space cutting measure. Typically the donut spare takes up much less space and is cheaper to manufacture than full size tires and wheels, which translates into more profit for the car makers. It’s quite a compromise and a loss for the consumer.

Can I Put A Full Size Spare On My Car?

Yes, but the question is: where do you carry and stow it? Years ago, cars had spare tire wells to fit the full size spare so that it was out of the way. This space has been eliminated in order to produce smaller cars (and increased profits for the carmakers). Looks like we’re stuck with donut spares. What's worse is that many new cars are doing away with spare tires altogether, opting for run-flat tires. But that's a topic for another day.